1. Field of the Invention
The present invention relates to a stepping motor, drive-control circuit preferably used as, for example, an image reading motor for a facsimile or the like.
2. Related Background Art
In a facsimile sheet conveying system and the like, a stepping motor has been generally used. As the driving systems for the stepping motor, a constant-current driving system and a constant-voltage driving system are used. For driving at a relatively low speed, a constant-voltage driving operation is often performed using a four-phase unipolar stepping motor in which the driving circuit can be simplified.
However, when a general four-phase unipolar stepping motor is used, current flows through all of the four-phase coils under the worst conditions so that equipment may be damaged by the excess increase of the temperature of the motor. The addition of a protective circuit for breaking current or the like with a thermal fuse is considered to prevent the damage during a software runaway malfunction. However, a cost increase is caused by the addition of the protective circuit, for example, in a protective circuit using the thermal fuse, and an exchange of a part was required for regeneration during a circuit operation.
Further, a problem occurs that when the motor is driven by the same driving force in low speed driving as that in high speed driving, the excessively large driving force results in a greater conveyance noise.